摘要：Large wood (LW) elements are often transported by rivers into
reservoirs during heavy rainfall events. Large wood has important
environmental attributes that benefit the diversification of riverine
ecosystems. There are several studies dealing with the transport and
behaviour of LW inside streams. However, during flood events, LW tends
to create jams or blockages at diverse hydraulic structures inside streams,
creating significant problems such as discharge limitations and increased
water levels. Even though knowledge on the effect of LW at bridges in rivers
with relatively high flow velocities starts to be available, the latter is hardly
applicable for reservoir approach flow conditions. Understanding LW
blockage processes at a reservoir spillway is essential regarding the safety
evaluation of a dam and the surrounding areas. The geomorphologic benefits
of wood for stream restoration depends also on our present ability to manage
jams and the risk they imply for civil structures when blocked. Therefore,
series of systematic laboratory experiments were conducted to analyse
blockage of floating stems at an ogee crested spillway equipped with piers.
Different LW characteristics were represented in a physical model with
cylindrical stems. Results associate the size of stem groups to blockage
probabilities and the effect blockages can have on the discharge capacity of
a spillway.
其他摘要：Large wood (LW) elements are often transported by rivers into reservoirs during heavy rainfall events. Large wood has important environmental attributes that benefit the diversification of riverine ecosystems. There are several studies dealing with the transport and behaviour of LW inside streams. However, during flood events, LW tends to create jams or blockages at diverse hydraulic structures inside streams, creating significant problems such as discharge limitations and increased water levels. Even though knowledge on the effect of LW at bridges in rivers with relatively high flow velocities starts to be available, the latter is hardly applicable for reservoir approach flow conditions. Understanding LW blockage processes at a reservoir spillway is essential regarding the safety evaluation of a dam and the surrounding areas. The geomorphologic benefits of wood for stream restoration depends also on our present ability to manage jams and the risk they imply for civil structures when blocked. Therefore, series of systematic laboratory experiments were conducted to analyse blockage of floating stems at an ogee crested spillway equipped with piers. Different LW characteristics were represented in a physical model with cylindrical stems. Results associate the size of stem groups to blockage probabilities and the effect blockages can have on the discharge capacity of a spillway.
